The effect of immunosuppression on chlamydial genital tract infection will be studied in an animal model system using guinea pigs and the agent of guinea pig inclusion conjunctivitis (Gp-ic). Immunosuppression produced by cyclophosphamide (Cy) will continue to be investigated, and the effect on cell-mediated immunity as well as humoral immunity will be monitored. The influence of Cy on altering pathogenesis of infection will be further investigated. Immunosuppression will also be studied by the use of anti-guinea pig thymocyte serum (ATS). ATS, produced in rabbits, will be administered to recipients infected in the genital tract with Gp-ic. The results will be compared to untreated control infected animals and infected animals receiving normal rabbit serum, and also to those already obtained for Cy. The feasibility of immunizing animals against chlamydial genital infection by administration of vaccine in the genital tract will be studied in female guinea pigs using an inactivated Gp-ic vaccine. Antibody response in genital secretions and sera will be studied with emphasis placed on ghe role of S-IgA antibodies in the secretions. The development of a C. trachomatis animal model system employing mice and the agent of mouse pneumonitis will be further investigated.